Todd Heitkamp, a National Weather Service meteorologist, said the line of storms appeared to coalesce into a derecho around.

A dangerous derecho is expected to form in parts of the Northern Plains and Upper Midwest on Monday, with wind gusts over 75 mph likely. A moderate threat for severe storms is in place for parts of South Dakota and Minnesota on Monday afternoon into the evening due to the threat of a derecho, a wind storm that can cause significant damage.

Millions of Americans across four US states are bracing for a derecho as officials sound alarms to prepare emergency supplies.